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In this paper, the Northeast China including the 3 provinces of Heilongjiang, Liaoning and Jilin was regarded as study area where maize, rice and soybean were main food crops. Simulation of spatial competition of the 3 crops under 4 future combined scenarios of IPCC CO2 emission and socio-economic development (urbanization rate and governmental purchasing price for food crops) was conducted for the year of 2030 by application of the FCS (farmer crop selection) model () and EPIC (environmental policy integrated climate) model. The 4 final scenarios were A2C1D1, A2C1D2, B2C2D1 and B2C2D2. A2C1D1 represented a combination scenario by IPCC A2 option, farmers having no income when going to city to do temporary work and prices for food crop purchased by government doubling. A2C1D2 meant a combination scenario by IPCC A2 option, farmers having no income when going to city to do temporary work and prices for food crop purchased by government quadrupling. B2C2D1 was a combination scenario by IPCC B2 option, farmers having income when going to city to do temporary work and prices for food crop purchased by government doubling. B2C2D2 denoted a combination scenario by IPCC B2 option, farmers having income when going to city to do temporary work and prices for food crop purchased by government quadrupling. In comparison with simulation results in 2009, the conclusions were: 1) For the first scenario of A2C1D1, percentage of maize acreage to total arable land decreased to 77.36% from 82.3%, and meanwhile there was an increase from 7.7% and 10% to 8.93% and 13.71% for soybean and paddy rice, respectively; spatially, maize acreage declined in the fringe areas between the Lesser Xing'an Mountain and the Haerbin Plain, but in the Liaohe Plain acreages of soybean and rice went up respectively. 2) For the second scenario of A2C1D2, percentage of maize acreage to total arable land decreased to 75.56% and meanwhile that of soybean and paddy rice increased to 9.52% and 14.92%, respectively; spatially the change was very similar to that of the scenario of A2C1D1. 3) For the third scenario of B2C2D1, due to a little bit higher urbanization rate than present and present purchasing price by government doubling, percentage of maize acreage to total arable land increased to 84.16%, and meanwhile soybean and paddy rice increased to 9.52% and 14.92%, respectively; maize acreage rose in the fringe areas between the Lesser Xing'an Mountain and the Haerbin Plain, while in the Liaohe Plain acreages of soybean and rice went down respectively, which was contrary to that of the A2C1D1scenario. 4) For the fourth scenario of IPCC B2C2D2, due to a little bit higher urbanization rate than present and present purchasing price by government quadrupling, percentage of maize acreage to total food crops acreage decreased to 80.06%, and meanwhile soybean and paddy rice increased to 9.01% and 10.93%, respectively. There was not obvious change in space. Since 2030 is not far from present, there are not very dramatic changes of food crops in space for all the 4 scenarios. We also don't consider extreme events' effect on spatial competition of food crops because cognition and judge of farmers will not be influenced by that. In terms of present practical situation in China, we deduce the scenarios of B2C2D1 and B2C2D2 maybe more accord with reality. Moreover, B2C2D2 will be more beneficial to optimizing agricultural layout. [ABSTRACT FROM AUTHOR]

Background: Reserved arable lands in China is of great significance for rationally allocating crop planting structures, alleviating the pressure of grain imports, and protecting food security. Owing to data acquisition limitations, obtaining the spatial distribution of reserved arable lands at large spatial scales is relatively rare, and there is little information on predicting the suitability, production capacity, and ecological effects of crop cultivation in reserved arable lands. This study obtained the distribution of reserved arable lands in China by applying restrictive factors, and used the Food and Agriculture Organisation of the United Nations (FAO) suitability index for eight crops to obtain a spatial distribution map of suitable crops, proposed a cropland ecological efficiency index (CEEI) to analyse the ecological impact of crop cultivation in reserved arable lands., Results: China possesses approximately 3.93 million hectares of viable reserved arable lands comprising primarily grasslands (67.68%), sandy land (8.11%), saline-alkali land (20.68%), and bare land (3.53%). The average CEEI for the eight crops under irrigation conditions ranges from 0.844 to 0.865, and that under rain-fed conditions (excluding rice) ranges from 0.609 to 0.779., Conclusion: We proposed the development of rain-fed agriculture with sorghum as the primary crop in the central part of Shanxi and Inner Mongolia, while promoting the cultivation of rapeseed and soybeans in the eastern parts of Heilongjiang, Jilin, and Inner Mongolia. Overall, the development of irrigation agriculture focusing on wheat and barley should be pursued only when water resources are guaranteed, particularly in north-western regions such as Gansu, Ningxia, Xinjiang, Qinghai, and Shaanxi. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)